1. Technical Field
The present invention relates to a printer that prints one dot line at a time using a line head, and to a control method for the printer.
2. Related Art
Printers such as thermal printers that print one dot line at a time using a fixed line head are typically used in POS printers. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-H08-34135 and Japanese Unexamined Patent Appl. Pub. JP-A-2002-248800.
FIG. 7 is a block diagram showing the configuration of a thermal printer according to the related art. As shown in FIG. 7, the thermal printer has a thermal head (line head) 101 composed of a plurality of heating elements arrayed in a line, a shift register 103 (shift register circuit) composed of n flip-flops, a latch (latch circuit) that temporarily latches the values of the shift register 103, a latch driver 102 composed of latches (latch circuits) that control heating the heating elements and a driver that is a transistor or other drive circuit, and a head control unit 104.
The head control unit 104 sends print data (serial data, input data) for one dot line to the shift register 103 (to the first flip-flop 103-1) synchronized to a clock signal CLK.
When sending the one dot line of print data is completed, the head control unit 104 sends a latch signal LAT to the latch driver 102. As a result, the print data for one dot line is latched in the latch driver 102 (that is, the data is temporarily stored). After one dot line of data is thus set, the head control unit 104 sends a strobe signal STB that defines the energize time of each heating element to the latch driver 102.
The latch driver 102 then energizes each heating element corresponding to a “1” in the latched data based on the strobe signal STB. Each energized heating element changes the color of the thermal paper used as the recording medium, and forms an image of one dot. The paper is then advanced the distance of one line by a paper feed mechanism including a motor and rollers. These steps repeat to sequentially print one line at a time.
The specifications for the number and density of the heating elements on the thermal head used in a thermal printer vary widely according to the application of the customer. This means that the circuit board must be changed according to the specifications of the thermal head, and different firmware is also required. The need for firmware and circuit boards designed and built to different specifications increases the development cost and complicates inventory management.
Furthermore, because the number of heating elements and the density of the heating element array cannot be detected automatically, a DIP switch could conceivably be provided on the circuit board and set according to the specifications of the thermal head. However, in addition to this requiring the operator, for example, to configure the DIP switch, there is also the possibility that the thermal head and DIP switch settings will not correspond correctly after parts are replaced or repaired because the number and the density of the heating elements are not readily apparent from the appearance of the thermal head. Another problem is the increase in the cost of the circuit board resulting from using a DIP switch.